Bruce Kreitler: Will pruning tree help grass underneath get more sun and grow?

A question I’ve had a lot last year, and am going to get more of this year, is “Can I prune my tree enough to be able to re-establish the grass that used to be under it?”

I’ve addressed the sunlight issue before, but with the way the climate has been for the past couple of years, a lot of turf was stressed more than usual. What this means is, if turf already was borderline beneath a tree, the added stress probably went ahead and took it out. I know I’ve stood on a lot more bare ground than normal in the past year or so, and most homeowners don’t care for big bald spots in the yard.

Before I get into the tree part of this, one thing I would like to point out is that the type of grass that was lost may have been part of the problem. Turf grasses have different tolerances for shade, meaning that varieties, such as St. Augustine, handle it better than say, standard Bermuda. If you are trying to grow a variety that doesn’t handle shade well, like Bermuda beneath your lush shade tree, part of trying to re-turf the area is probably going to involve using a different variety of grass.

By the way, there are newer strains of Bermuda grass that tolerate more shade (which for plants, this really means less light) than even St. Augustine. Before you go to the expense involved with the prep and replacement of lost lawn, it’s a good idea to get with a knowledgeable “turf guy (or girl as the case may be)” and find out which grass would work best for you.

Getting back to the trees, and possibly pruning them to make more light (which grass can’t grow without) available to them, this can be done. The question is how much of the tree will you have to remove to get enough light, and what is the overall effect on the tree of that amount of foliage/limb removal?

Being a tree guy, I like to approach this kind of work with the goal of getting enough light through, under, or around the tree, to the ground, but without doing anything that I consider permanently damaging to the tree itself. Sometimes, one good way to get light on the grass is to simply raise the canopy of the tree. Depending what may in front or back of the tree, this simple operation may get enough evening or morning sun beneath the tree without damaging the middle of the day shade canopy (this is important when it’s more than 100 degrees outside).

In the instances when raising the canopy or just basic maintenance pruning isn’t enough to get light beneath the tree — and there are lot of them, we approach that from a different direction. In those cases, what we will do is go ahead with the normal pruning and when that is finished, look the tree over and selectively prune to put some “holes in the canopy.” We do this by removing some of the smaller branches that reach from the interior of the tree all the way to the outer edge of the canopy. The reason for this is that we can get some light through, but without removing any major limbs or structure.

After all, the tree may live for many years yet, and if it’s reached a size where it can cast enough shade to interfere with turf, it’s probably large enough that removing big chunks of it will look very bad and/or be unhealthy for the tree.